Cam understanding

Discussions around the CAM Add-On of QCAD.

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Dreamaker
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Cam understanding

Post by Dreamaker » Sun Jul 16, 2017 5:55 pm

I am somewhat a self taught person, a work in progress, I challenge myself with things that probably most people don't mess with. I have Qcad/cam and on the most part, having fun with it. When I originally bought Qcad, I used it for my CNC Laser engraving and liked it, you didn't go through bunch of steps to do simple things. I recently purchased a 3040 CNC Router/Mill from China, and bought Mach3 software for my controller. Well I found I needed a Cam converter to go from DXF to G-code. It was suggest to me from the person that introduced me to Qcad that it had its own cam portion section, so I purchased the Qcad/cam program. When I bought the original Qcad, I also bought the paper manual, which has been very helpful and is worth the price to have. OK! I don't understand how and what most function do in the cam add on. I looked in the manual and looked around some what trying to find reference on what the cam function do and understand the proper setting. What I have been doing at this point, is trying to use common sense and trial and error and mimic some of the setting that have been pasted on to me to make some things work. But I have had some error and don't understand why. Is there a quick reference manual, book, location in English, so I can understand why I am setting things these ways and what I am doing wrong.

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andrew
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Re: Cam understanding

Post by andrew » Mon Jul 17, 2017 8:04 am

Dreamaker wrote:But I have had some error and don't understand why. Is there a quick reference manual, book, location in English, so I can understand why I am setting things these ways and what I am doing wrong.
We have a brief step-by-step tutorial about preparing drawings and creating toolpaths at:

http://qcad.org/doc/qcadcam/QCADCAM_Tutorial_en.pdf

Feel free to post any specific problem together with the DXF file and the (undesired) output in this forum, so we can help effectively.

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Dreamaker
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Re: Cam understanding

Post by Dreamaker » Mon Jul 17, 2017 2:15 pm

Thank You that was very helpful, one more thing! In the widgets at the top the are buttons with symbols in them, what are they and what is their function. Or can you point me in the direction where they are explained.

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andrew
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Re: Cam understanding

Post by andrew » Mon Jul 17, 2017 4:32 pm

The CAM specific buttons are explained in the tutorial linked above. All tools are also briefly documented with icon, tool name and description in the user reference manual (Help > Reference Manual) or online at: http://www.qcad.org/doc/qcad/latest/reference/en/

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Dreamaker
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Re: Cam understanding

Post by Dreamaker » Mon Jul 17, 2017 6:55 pm

I just did some gear tryouts Lexan plastic, one large gear and three small gears where the teeth mesh with each other. I seems where I am having issues understanding the function, is in the “lead in” area.
All four center holes were the same size 8mm using a 2mm two flute end mill, and used the same profile for them. The thing that confused me is the big gear the center hole was a little out of round, but the three small gears the center holes the “ lead in/out” took a good chunk out of the gear body unlike the big gear which uses the same profile. I know it is about tweaking the lead in and understand how it works. Do you have info about the different choices in the “lead in” menu on what they do? The difference between, “Normal, Extension. Half Circle, Quarter Circle, Eighth Circle, Lead in Length and Over Cut”. If you will notice on the small gear, one of the teeth also got clipped due to lead in/out. Also the center hole the choice was inside and the gear teeth was outside.
Is there some document that has more detail, the other document was very helpful but limited info.
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andrew
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Re: Cam understanding

Post by andrew » Mon Jul 17, 2017 7:01 pm

Please attach always your DXF file for each problem you encounter. I will then be able to point you to the problem. Thanks.

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Dreamaker
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Re: Cam understanding

Post by Dreamaker » Mon Jul 17, 2017 7:07 pm

Disregard my last message, I did not see your latest message to me pointing me in the direction of the info.

Thank You

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Dreamaker
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Re: Cam understanding

Post by Dreamaker » Tue Jul 18, 2017 1:29 pm

Is there more information on the area of Leads, it seems that is where most of my problem are from. I don't understand what the differences and effect to the object like Normal verses Extensions. Also the effect and advantages of using, Half Circle, Quarter Circle and Eighth Circle, of what it really does. The picture of the small gear center hole, may be the result of using Inside/Eighth Circle, the confusing part is why did it not do the same thing to the large gear center hole, all four object used the same profile. If there is additional information or details on usage of Leads, please point me in that direction.

Again sorry for all the trouble! I am a work in progress, but I really like the program.

Thank You

Dan

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Husky
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Re: Cam understanding

Post by Husky » Wed Jul 19, 2017 2:27 am

Hi Dan,
Dreamaker wrote:I don't understand what the differences and effect to the object like Normal verses Extensions. Also the effect and advantages of using, Half Circle, Quarter Circle and Eighth Circle, of what it really does.
Long story very short:
Think about the shape of your cutter (Circle!), think about the path which this circle needs to follow to cut inside or outside your desired shape. Think about a shape in your drawing with sharp(!) edges like a square or a rectangle. There is no information in the drawing to tell the cutter where to start or to stop to reach the goal of a precisely sharp 90 degree angle.

Now the CAM kicks in and will calculate the missing information for the correct path. This function is called "Cutter radius compensation". You have to give the CAM the Cutter diameter and what kind of calculation (Leads) to you like to see. E.g. Extensions means the CAM will calculate and add extension lines to the shape of your CAD drawing for the start and the end point of the shape.

On this screenshot you can see a Normal and an Extensions situation. The red lines shows why we need this "Cutter radius compensation". Without it you would be forced to finish this workpiece manually and that can't be the idea of having a CNC :wink:
Husky-2017.07.18-05.png
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Dreamaker
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Re: Cam understanding

Post by Dreamaker » Thu Jul 20, 2017 9:19 pm

I figured rather that talk about it, I should do something. So, on Lexan I cut six test circles, each set differently from Normal to 1/8th Circle to see how it would react during routering. I did inside cut and outside cut circles and also did inside boxes, to see what happens. I use as a control program Mach3 and and noticed something. Like Andrew said you need also the set the tool size on the control program, this is true. I am assuming the Qcam/cam tells the controller what tool to look for in the G-code. I did the circles and the inside cut came out 1mm larger then the drawing, and the outside cut come out 1mm smaller. I could not figure it out why, I physically measured the cutter and entered it into the tool information. In tool information you give it a tool number and put in the Dia. and the length, and save it. Well, I found out that no matter what tool value or tool number you enter or show on the controller it will not compensate the size or tool showing. For example for my cut I created tool # 4 and ran the job, the size was wrong again. Being a newbie and not totally understanding G-code I gave it a look. I seen a T-code, Which was T1, not sure I changen it to T4 which was my tool number and ran the job and the dimension came out correct. Point is: even though you give a tool size in Qcad/cam and enter a tool size on the controller program tool information, it will go to the tool that the G-code shows the T#, that is if you have been saving your tool information. If you have not been saving your tool information, then it will recognize the entry in controller tool information input.

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Dreamaker
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Re: Cam understanding

Post by Dreamaker » Sun Jul 23, 2017 3:30 pm

Well, things are seeming to start coming together. Doing some testing on different shapes and material, and things are making more sense, figuring out what I can and cannot do. Making some cause and effect examples for my reference.

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Re: Cam understanding

Post by jamby » Tue Jul 25, 2017 8:55 pm

Dan

Don't know if this is proper etiquette here but I have used the program "cnc discriminator" for years its available here http://www.cncedit.com/
It may just be that I am more familiar with it then any thing else but I like the 3D views and edit on the fly ability's. Selecting a line on the screen will highlight the line of code that drove it. Only problem is its Windoze only.


Jim

Oh, did you figure out the "On /outside / inside " setting in the "Add profile toolpath" , near the bottom left "Side / Direction" heading. That will control which direction the cutter will ride on.

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